Heat sink and thermal interface having shielding to attenuate electromagnetic interference

ABSTRACT

Heat sink and electrically non-conducting thermal interface having shielding to attenuate electromagnetic interference. The interface comprises a generally planar substrate having first and second outwardly facing surfaces. The substrate is formed from a material, preferably a polymer, that is both thermally conductive and has a high dielectric strength. Formed upon the outwardly facing surfaces are layers of a thermally conductive compound for facilitating heat transfer. The invention further comprises an improved heat sink comprising a baseplate coupled with a folded-fin assembly, the latter being compressively bonded thereto via a pressure clip and pressure spreader assembly. The base plate is attachable to a heat-dissipating component, and may optionally include a ground contact connection for use with components that are not already grounded.

BACKGROUND OF THE INVENTION

Interface systems for use in transferring heat produced from aheat-dissipating electronic component to a heat dissipator or heat sinkare well-known in the art. In this regard, such electronic components,the most common being computer chip microprocessors, generate sufficientheat to adversely affect their operation unless adequate heatdissipation is provided. To achieve this end, such interface systems arespecifically designed to aid in the transfer of heat by forming aheat-conductive pathway from the component to its mounting surface,across the interface, and to the heat sink.

In addition to facilitating the transfer of heat, certain applicationsfurther require electrical insulation. Accordingly, such interfacesystems are frequently further provided with materials that are not onlyeffective in conducting heat, but additionally offer high electricalinsulating capability. Among the materials frequently utilized toprovide such electrical insulation are polyimide substrates, and inparticular KAPTON (a registered trademark of DuPont) type MT.

Exemplary of such contemporary thermal interfaces are THERMSTRATE andISOSTRATE (both trademarks of Power Devices, Inc. of Laguna Hills,Calif.). The THERMSTRATE interface comprises thermally conductive,die-cut pads which are placed intermediate the electronic component andthe heat sink so as to enhance heat conduction therebetween. TheTHERMSTRATE heat pads comprise a durable-type 1100 or 1145 aluminumalloy substrate having a thickness of approximately 0.002 inch (althoughother aluminum and/or copper foil thickness may be utilized) that iscoated on both sides thereof with a proprietary thermal compound, thelatter comprising a paraffin base containing additives which enhancethermal conductivity, as well as control its responsiveness to heat andpressure. Such compound advantageously undergoes a selectivephase-change insofar the compound is dry at room temperature, yetliquifies below the operating temperature of the great majority ofelectronic components, which is typically around 51E° C. or higher, soas to assure desired heat conduction. When the electronic component isno longer in use (i.e., is no longer dissipating heat), such thermalconductive compound resolidifies once the same cools to below 51E° C.

The ISOSTRATE thermal interface is likewise a die-cut mounting pad thatutilizes a heat conducting polyimide substrate, namely, KAPTON (aregistered trademark of DuPont) type MT, that further incorporates theuse of a proprietary paraffin based thermal compound utilizing additivesto enhance thermal conductivity and to control its response to heat andpressure. Advantageously, by utilizing a polyimide substrate, suchinterface is further provided with high dielectric capability.

Additionally exemplary of prior-art thermal interfaces include thosedisclosed in U.S. Pat. No. 5,912,805, issued on Jun. 15, 1999 to Freuleret al. and entitled THERMAL INTERFACE WITH ADHESIVE. Such patentdiscloses a thermal interface positionable between an electroniccomponent and heat sink comprised of first and second generally planarsubstrates that are compressively bonded to one another and have athermally-conductive material formed on the outwardly-facing opposedsides thereof. Such interface has the advantage of being adhesivelybonded into position between an electronic component and heat sink suchthat the adhesive formed upon the thermal interface extends beyond thejuncture where the interfaces interpose between the heat sink and theelectronic component.

The process for forming thermal interfaces according to contemporarymethodology is described in more detail in U.S. Pat. No. 4,299,715,issued on Nov. 10, 1981 to Whitfield et al. and entitled METHODS ANDMATERIALS FOR CONDUCTING HEAT FROM ELECTRONIC COMPONENTS AND THE LIKE;U.S. Pat. No. 4,466,483, issued on Aug. 21, 1984 to Whitfield et al. andentitled METHODS AND MEANS FOR CONDUCTING HEAT FROM ELECTRONICCOMPONENTS AND THE LIKE; and U.S. Pat. No. 4,473,113, issued on Sep. 25,1984 to Whitfield et al. and entitled METHODS AND MATERIALS FORCONDUCTING HEAT FROM ELECTRONIC COMPONENTS AND THE LIKE, the contents ofall three of which are expressly incorporated herein by reference.

In addition to the construction of thermal interfaces, there havefurther been advancements in the art with respect to the thermalcompositions utilized for facilitating the transfer of heat across aninterface. Exemplary of such compounds include those disclosed in U.S.Pat. No. 6,054,198, issued on Apr. 25, 2000 to Bunyan et al. andentitled CONFORMAL THERMAL INTERFACE MATERIAL FOR ELECTRONIC COMPONENTS,and U.S. Pat. No. 5,930,893, issued on Aug. 3, 1999 to Eaton andentitled THERMALLY CONDUCTIVE MATERIAL AND METHOD OF USING THE SAME, theteachings of which are expressly incorporated by reference.

In addition to being able to facilitate the transfer of heat and provideelectrical insulation, many interface systems additionally employ agrounded substrate formed from a conductive material, such as copper, tosuppress radiated emissions, namely electromagnetic interference (EMI),generated in high frequency transistor applications. In this regard,such grounded substrate is utilized to minimize capacitance to the heatsink to which it is attached, as well as to provide shieldingeffectiveness and attenuation of radiated EMI. With respect to thelatter, it has been shown that electrically grounded copper substratescan provide shielding effectiveness to 60 dB at 1000 KHz, which is anattenuation percentage of 99.9%.

One such commercially-available thermal interface incorporating agrounded conductive substrate is EMI-STRATE (a registered trademark ofPower Devices, Inc. of Laguna Hills, Calif.). Such interface comprises agrounded copper substrate sandwiched between two polyimide filmsubstrates, the latter being comprised of KAPTON-type MT. The exteriorsides of such interface are further coated with a proprietary thermalcompound to thus facilitate the transfer of heat away from theelectronic component to a heat sink.

Notwithstanding the effectiveness of thermal interfaces currently inuse, a substantial need exists in the art for an interface that providesgreater EMI attenuation, shielding effectiveness, and thermalconductivity. In this regard, newer electronic componentry continues tohave ever increasing power dissipation and EMI emission. While suchelectronic componentry typically is constructed and/or packaged to beelectrically isolated, the aforementioned increases in power dissipationand EMI emission currently present drawbacks that must be addressed ifsuch componentry is to perform optimally. Additionally, as such advancesare made in such componentry, it is certain that the aforementionedconcerns regarding radiated emission and power dissipation will continueto create a demand for an interface system that can adequately addressthe same.

Prior art interface systems, however, are ill-suited to meet such needsinsofar as such interface systems, because of their multiple-layerconstruction, substantially reduces the flow of heat thereacross. Inthis regard, it has been found that the use of thermal interface systemshaving six layer construction does not provide desirable heat transferfrom a given electronic component to a heat sink. Moreover, not onlydoes each individual layer impede heat flow, but, as those skilled inthe art will appreciate, each interface of adjacent layers additionallyinhibits heat flow. In this respect, each layer contributes threedistinct impediments to heat flow, namely, each layer introduces thematerial of which the layer itself is comprised, as well as the twointerfaces at either surface of the layer. Thus, it will be appreciatedthat it is highly desirable to minimize the number of layers, andconsequently the number of interfaces, comprising such interface system.In addition to the foregoing, it should be noted from a practicalstandpoint that manufacturing such interface systems having multiplelayers is expensive.

In addition to the need for improved interface systems is the need forimproved heat sinks to be used therewith that are capable of moreeffectively and efficiently dissipating the heat transfer thereto. Inthis regard, most heat sinks in use, which are typically fabricated fromextruded aluminum, are formed to have a base with a plurality of finsextending therefrom. The fins are equidistantly spaced from one anotherand are formed to have sufficient surface area to dissipate the heatinto the surrounding air. In this respect, a fan is frequently used toassure adequate circulation of air over the fins, so as to maintaindesirable heat dissipation therefrom.

Unfortunately, however, the number of fins and the spacing therebetweenis limited by the aluminum extrusion process. As is well-known, finsspaced closer together than 0.2 inches tends to block natural convectionair flow and cannot be optimized for use in forced convection.Additionally, conventional extrusion technology limits the amount ofsurface area, namely, the height of the fins of the heat sink, whichfurther constrains heat removal. In this respect, it is well-known thatthe amount of surface area is proportional to the amount of heat thatcan be removed. Hence, a decrease in surface area thus translates intolimited heat removal.

To partially address the aforementioned inadequacies with extrudedaluminum heat sinks has been the introduction of folded-fin heat sinks.Such assemblies comprise a relatively thin base section and a set offins folded into corrugated sections mounted thereon. The base sectionis typically formed to be either very thin to reduce mass or,alternatively, thicker to act as a heat spreader. The folded finscoupled to the base act as a heat-transfer area, allowing a stream offorced air to remove heat from the base. Currently, such folded-fin heatsinks offer the maximum potential in surface area and reduced weight. Inthis respect, thermal resistance as low as 0.40E° C./W can be reachedwith folded-fin assemblies in forced-air cooling at 500 ft/min of airvelocity. Moreover, in utilizing a corrugated piece of aluminum orcopper, there is thus eliminated the restrictions otherwise faced in theextrusion process.

Notwithstanding the desirability of such folded-fin heat sinks, the samestill suffer from the drawback of failing to achieve optimal heattransfer and dissipation insofar as current folded-fin heat sinks failto achieve optimal heat transfer from the base to the folded-finassembly coupled thereto. As such, the maximum amount of heat that couldotherwise be dissipated by the assembly is not attained.

Accordingly, there is a need in the art for a thermal interface thatprovides greater thermal conductivity and greater electrical insulationthan prior art interfaces. There is additionally a need in the art forsuch a thermal interface that is of low cost, easy to manufacture, andmay be readily utilized with existing componentry requiring theintegration of a thermal interface system. Moreover, there is a need inthe art for an improved heat sink that is more effective and efficientat dissipating heat transferred thereto from an electronic component.There is further a need for such an improved heat sink that isparticularly more effective in transferring heat from a given heatsource to the fins or other apparatus by which the same is dissipated.

BRIEF SUMMARY OF THE INVENTION

The present invention specifically addresses and alleviates theaforementioned deficiencies in the art. Specifically, the presentinvention is directed to an interface system for use with electroniccomponentry that has superior electrical insulation and thermalconductivity properties than prior art systems. In the preferredembodiment, the interface system of the present invention comprises thecombination of a generally planar substrate, preferably being comprisedof a non-conductive material having a high dielectric strength. Theplanar substrate defines two outwardly facing flatwise surfaces that areconfigured to mate with the interface surfaces formed on the electroniccomponent and the interface surface formed on the heat dissipator orheat sink, on the other surface Each respective outwardly facing surfacehas formed thereon a layer of a thermally conductive compound having ahigh degree of thermal conductivity to thus further facilitate thetransfer of heat. In a preferred embodiment, such compound is preferablyformed to have selective phase-change properties whereby the compositionexists in a solid phase at normal room temperature, but melts, andtherefore assumes a liquid phase, when subjected to the elevatedtemperatures at which the electronic component usually operates.

The present invention further includes an improved heat sink that ismore efficient and effective in dissipating heat transferred thereto viaan electronic component. Specifically, such improved heat sink comprisesthe combination of a base plate attachable to a heat-dissipatingcomponent and a folded-fin assembly compressively attached thereto. In apreferred embodiment, the heat sink is provided with one or morepressure clips (or other fastener arrangement) detachably fastenable tothe baseplate that apply a compressive force, via a pressure spreaderengagable therewith, against the folded-fin assembly that causes theassembly to remain compressively bonded with the baseplate from whichthe heat to be dissipated is received. To further facilitate thetransfer of heat from the baseplate to the folded-fin assembly, there ispreferably provided upon the baseplate a layer of a thermally-conductivecompound having selective phase-change properties (i.e., liquefiesduring the operational temperature of the electronic component coupledto the heat sink), to eliminate any air gaps or voids between thebaseplate and folded-fin assembly that would otherwise impede thetransfer of heat. Alternatively, to the extent a greater degree ofelectrical isolation is desired, a thermal interface having a highdielectric capability may be interposed between the baseplate andfolded-fin assembly.

The present invention thus provides a thermal interface system thatprovides both electrical insulation and sufficient thermal conductivityto effectively facilitate the removal of heat therefrom more so thanprior art interface systems.

The present invention further provides a thermal interface havingelectrical isolation capability that utilizes a minimal number of layersin the construction thereof.

Another object of the present invention is to provide a thermalinterface that is relatively simple and inexpensive to manufacturecompared to prior art interface systems, and may be readily and easilyutilized in a wide variety of commercial applications.

Another object of the present invention is to provide an improved heatsink that is more effective and efficient at dissipating heattransferred thereto from an electronic component, and especially more sothan conventional heat sinks formed from extruded aluminum.

Another object of the present invention is to provide an improved heatsink that is capable of more effectively transferring heat receivedthereby to the heat-dissipating component thereof than prior art heatsinks.

A still further object of the present invention is to provide animproved heat sink that is of simple construction, may be readily andeasily fabricated from existing materials well-known to those skilled inthe art, is relatively inexpensive, and may be readily and easilyutilized in numerous commercial applications.

BRIEF DESCRIPTION OF THE DRAWINGS

These as well as other features the present invention will become moreapparent upon reference to the drawings wherein:

FIG. 1 is an exploded perspective view of an extruded heat sinkpositioned for attachment to an electronic component showing a preformedthermal interface pad of the present invention being disposedtherebetween;

FIG. 2 is a cross-sectional view taken along line 2?2 of FIG. 1;

FIG. 3 is a perspective view of the respective layers comprising thethermal interface of the present invention;

FIG. 4 is a perspective view of the respective layers comprising a priorart thermal interface;

FIG. 5 is a perspective view of an improved heat sink constructed inaccordance to a preferred embodiment of the present invention; and

FIG. 6 is an exploded perspective view of the heat sink depicted in FIG.5.

DETAILED DESCRIPTION OF THE INVENTION

The detailed description set forth below in connection with the appendeddrawings is intended merely as a description of the presently preferredembodiment of the invention, and is not intended to represent the onlyform in which the present invention may be constructed or utilized. Thedescription sets forth the functions and sequence of steps forconstruction and implementation of the invention in connection with theillustrated embodiments. It is to be understood, however, that the sameor equivalent functions and sequences may be accomplished by differentembodiments that are also intended to be encompassed within the spiritand scope of the invention.

Referring now to the drawings, and initially to FIG. 1, there is shown athermal interface 10 constructed in accordance with one embodiment ofthe present invention. The thermal interface 10 is specifically designedand configured to facilitate the transfer of heat away from anelectronic component 12 to a heat sink 14. In addition to facilitatingthe transfer of heat, the thermal interface 10 of the present inventionis further provided with electrical insulating capability to thussubstantially electrically isolate the electronic component 12 duringthe operation thereof.

As illustrated, the thermal interface 10 is specifically designed andadapted to be interposed between the electronic component 12 and heatsink 14. As is well-known, such heat sink 14 is provided with structures0such as fins or other protuberances 14 a having sufficient surface areato dissipate the heat into the surrounding air. Although not shown, tofacilitate such heat dissipation, a fan is frequently utilized toprovide adequate air circulation over the fins or protuberances 14 a.

Preferably, the thermal interface 10 is die-cut or pre-formed to have ashape or footprint compatible with the particular electronic componentand/or heat sink to thus enable the thermal interface 10 to maximizesurface area contact at the juncture between the electronic component 12and heat sink 14. Alternatively, the thermal interface 10 of the presentinvention may also be manually cut from a sheet of interface material,similar to other interface pads currently in use, so as to provide acustom fit between a given electronic component and heat sink.

Referring now to FIG. 2, there is shown a cross-sectional view of thethermal interface 10 of the present invention. As illustrated, thethermal interface 10 is comprised of three layers 16-20. The first layer16 comprises a thermally conductive compound formulated to facilitateand enhance the ability of the interface 10 to transfer heat away fromthe electronic component to the heat sink. Similar to other prior artcompositions, such layer 16 is preferably formulated to have certaindesired phase-change properties. Specifically, at room temperature,i.e., when the electronic device is not operating, the layer of thermalcompound 16 remains substantially solid.

Referring now to FIG. 2, there is shown a cross-sectional view of thethermal interface 10 of the present invention. As illustrated, thethermal interface 10 is comprised of three layers 16-20. The first layer16 comprises a thermally conductive compound formulated to facilitateand enhance the ability of the interface 10 to transfer heat away fromthe electronic component to the heat sink. Similar to other prior artcompositions, such layer 16 is preferably formulated to have certaindesired phase-change properties. Specifically, at room temperature,i.e., when the electronic device is not operating, the layer of thermalcompound 16 remains substantially solid. The thermally conductivecomposition may take any of those disclosed in Applicant's copendingpatent application entitled PHASE CHANGE THERMAL INTERFACE COMPOSITIONHAVING INDUCED BONDING PROPERTY, filed on Apr. 12, 2001, and assignedapplication Ser. No. 09/834,158, and Applicant's co-pending patentapplication entitled GRAPHITIC ALLOTROPE INTERFACE COMPOSITION ANDMETHOD OF FABRICATING THE SAME, filed on May 18, 2000, and assignedapplication Ser. No. 09/573,508, the teachings of which are expresslyincorporated herein by reference. Such thermal compounds have thedesirable phase-change properties of assuming a solid phase at normalroom temperature, but liquify at elevated temperatures of approximately51° C. or higher, which is typically just below the operatingtemperatures at which most electronic components are intended tooperate. It should be understood, however, that a wide variety ofalternative thermally conductive materials and compounds are availableand readily known to those skilled in the art which could be deployedfor use in the practice of the present invention.

The second layer 18 is a generally planar substrate layer provided withan outwardly facing side and an inwardly facing side, the latter beingbonded to the thermal component layer 16. Preferably, the substrate 18is formed from a material that is both thermally conductive and has highdielectric strength. In a preferred embodiment, a substrate isfabricated from a polymer and preferably a polyimide. Not by way oflimitation, one such highly preferred polyimide substrate includesKAPTON-type MT. However, other similar materials well-known to thoseskilled in the art may also be utilized, including ULTEM, a registeredtrademark of General Electric Corporation.

Advantageously, by using a substrate formed of a material having a highdielectric strength, there is thus provided a high degree of electricalinsulation. Along these lines, while the interface of the presentinvention is specifically designed and adapted to be utilized withelectronic componentry that already is electrically isolated, such addedelectrical insulation, as provided by the substrate 18, additionallyensures such electrical isolation, which as those skilled in the artwill recognize is frequently required in such applications.

To further facilitate and enhance the thermal performance of the thermalinterface 10 of the present invention, there is preferably provided asecond layer 20 of a thermally conductive compound formed upon theoutwardly facing surface of substrate 18. As with first layer 16, secondlayer 20 is preferably formulated to have certain desired phase-changeproperties, namely, assumes a solid phase when the electronic componentis not operating, but liquifies when subjected to the operatingtemperature of the electronic component, so as to ensure that any voidsor gaps formed by surface irregularities present upon the surface of theheat sink become filled, thereby maintaining a generally continuousmechanical contact to thus facilitate the transfer of heat to the heatsink coupled therewith.

As will be recognized by those skilled in the art, the interface 10 ofthe present invention, because of its novel construction, will only befabricated from three layers of material, namely, the first layer ofthermal compound 16, intermediate substrate 18 and second layer ofthermal compound 20, perspectively illustrated in FIG. 3. Suchconstruction, due to the minimal amount of layers utilized, isspecifically configured for optimal heat transmission therethrough, andthus is ideally suited for application as a thermal interface forfacilitating heat transfer from an electronic component to a heat sink.As those skilled in the art will appreciate, by eliminating additionallayers of material, which are typically present in prior art interfaces,there is thus facilitated the performance of heat transfer from theelectronic component to a heat sink. More specifically, it is well-knownthat the rate of heat transfer through such interface is reduced by eachlayer added thereto.

In contrast, as depicted in FIG. 4, there is shown a prior art interface26 having a seven-layer construction. The layers comprising the priorart interface 26 comprise, from bottom to top, a first or externalthermal compound layer 28, a first non-conductive substrate 30, a firstor internal adhesive layer 32, a layer of conductive material 34, asecond internal adhesive layer 36, a second non-conductive substrate 38,and a second external thermal compound layer 40. As discussed above,such multi-layer construction substantially reduces the rate of heattransfer therethrough, with the addition of each additional layerproviding that much more of an impediment in achieving the desiredthermal conductivity. Additionally, by using fewer layers, the thermalinterface 10 of the present invention is provided with a reducedthickness than such prior art interfaces, which, as a result, evenfurther enhances the flow of heat therethrough.

Referring now to FIGS. 5 and 6, and initially to FIG. 5, there is shownan improved heat sink 50 constructed in accordance to a preferredembodiment of the present invention. As shown, the heat sink 50comprises the combination of a baseplate 52 and a folded-fin assembly60, the latter being compressively mounted upon an electricallyinsulated platform surface 52 a formed on the baseplate 52 (shown inFIG. 6), via a pair of pressure clips 68 a, 68 b and electricallyinsulated pressure spreaders 64 a, 64 b. In order to provide the desiredelectrical insulation, the platform surface 52 a may have formed thereona sheet of electrically insulated material, such as KAPTON-type MT.Similarly, the pressure clips 68 a, 68 b will preferably be formed fromelectrically nonconductive materials such as fiberglass, or other likematerials.

The baseplate 52 is provided with a plurality of apertures 54 to enablethe same to be fastened, via bolts and the like, to a givenheat-dissipating component (not shown). The baseplate 52 further hasformed thereon opposed pairs of slots 56 a, a′ and 56 b, b′ that aredesigned and configured to receive respective ones of pairs of feet 70a, a′ and 70 b, b′ formed upon pressure clips 68 a, 68 b, more clearlyseen in FIG. 6. As will be appreciated by those skilled in the art,slots 56 a, a′ and 56 b, b′ provide points of leverage by which pressureclips 68 can impart a downwardly compressive force, via pressurespreader 64 a, 64 b, upon the folded-fin assembly 60, and moreparticularly the upper folds 60 b thereof. The baseplate 52 ispreferably formed from a material having excellent thermally conductiveproperties, such as aluminum and other like metals.

The folded-fin assembly 60 preferably comprises a unitary piece ofcorrugated metal, such as aluminum or other like materials well-known tothose skilled in the art, that have ideal heat-dissipating properties.As illustrated, the folded-fin assembly 60 is formed to have a generallyserpentine configuration such that the same is provided with a pluralityof downwardly facing bends 60 a that are oriented to mate with theelectrically insulated upper platform surface 52 a of baseplate 52, moreclearly seen in FIG. 6, and a plurality of upwardly oriented folds 60 b,the latter being forced compressively downward via pressure clips 68 a,68 b, and pressure spreader 64 a, 64 b.

As will be recognized by those skilled in the art, by using a folded-finassembly 60, the heat sink 50 is thus provided with a heat-dissipatingcomponent that is not limited by prior art extrusion processes. As iswell-known, prior heat sinks formed from extruded aluminum possesssubstantial limitations insofar as most extrusion processes limit theheight of such fins formed thereon to dissipate heat, as well as thespacing therebetween. Such limitations do not apply to the folded-finassembly 60, in contrast, by virtue of having fins folded into suchcorrugated sections 60 a, 60 b.

To maximize and facilitate physical contact, and thus enhance thermalconductivity between the folded-fin assembly 60 and baseplate 52, thereare provided pressure clips 68 a, 68 b and pressure spreaders 64 a, 64 bthat cooperate to impart a downwardly compressive force upon theoutwardly extending bends 60 b of the folded-fin assembly 60 thusforcing the folded-fin assembly to remain firmly seated and compressedagainst the baseplate 52. In the preferred embodiment shown, eachpressure clip 68 a, 68 b is provided with downwardly extending legs 72a, a′ and 72 b, b′ having outwardly extending feet 70 a, a′ and 70 b, b′formed at the distalmost ends thereof. The legs 72 are connected to oneanother via an elongate segment defined by downwardly-biased sections 74and mid-portion 76. As will be readily appreciated by those skilled inthe art, when the feet 70 of each respective pressure clip 68 a, 68 bare received within those dedicated slots 56 formed upon baseplate 52,such downwardly biased sections 74 and mid-portion 76 are caused toimpart the aforementioned downwardly compressive force.

Pressure spreaders 64 a, 64 b, which are preferably electricallyinsulated, are provided to impart a more even distribution of forceabout the upwardly extending bend 60 b of folded-fin assembly 60. Asshown, the pressure spreaders 64 a, 64 b preferably comprise elongatebeams that are designed and configured to align with downwardly-biasedsections 74 and mid-portion 76 of each respective pressure clip andbecome sandwiched between the clip 68 and the top fold 60 b offolded-fin assembly 60. Advantageously, by compressively bonding thefolded-fin assembly 60 against baseplate 52, thermal conductivity and,ultimately, heat dissipation is maximized and allows for greater heattransfer than prior art heat sinks.

To further facilitate the transfer of heat, there is optionally providedupon the upper platform surface 52 a of baseplate 52 a layer ofthermally conductive compound formulated to have the aforementioneddesired phase-change properties to thus ensure maximum mechanicalcontact between the folded-fin assembly 60 and baseplate 52.Alternatively, to the extent desired, an interface pad or other likesystem may be positioned upon the platform surface 52 a to providefurther desired properties (e.g., electrical insulation) in addition tofacilitating the transfer of heat.

In yet another optional embodiment of the present invention, base plate52 maybe provided with a ground contact connection 78, shown in phantomin FIGS. 5 and 6, to thus enable an electronic utilized therewith tobecome electrically grounded. Along these lines, while most electroniccomponentry typically in use is constructed and/or packaged to beelectrically isolated, to the extent such componentry is not grounded,ground contact connection 58 will thus facilitate that end. It will bereadily recognized by those skilled in the art, however, that in suchapplications, base plate 52 will be for the heat sink 50 will furtherinclude an electrically insulated pad or layer, such as 80 depicted inphantom in FIGS. 5 and 6, to ensure electrical isolation of the baseplate 52. In this respect, it is contemplated that such optional pad orlayer 80 may take the form of an interface pad or other like systemthat, in addition to providing electrical insulation, can furtherfacilitate the transfer of heat.

Although the invention has been described herein with specific referenceto a presently preferred embodiment thereof, it will be appreciated bythose skilled in the art that various additions, modifications,deletions and alterations may be made to such preferred embodimentwithout departing from the spirit and scope of the invention. Forexample, with respect to the improved heat sink of the presentinvention, any of a variety of mechanisms may be utilized to impart thecompressive force against the folded-fin assembly whereby the latter iscaused to be compressively bonded to the baseplate coupled therewith.Additionally, upper platform surface 52 a need not necessarily be formedto be electrically insulated, but may simply comprise an outwardlyfacing surface of the baseplate 52. Accordingly, it is intended that allreasonably foreseeable additions, modifications, deletions andalterations be included within the scope of the invention as defined inthe following claims.

What is claimed is:
 1. A thermal interface for facilitating heattransfer from an electronic component to a heat sink and suppressingelectromagnetic interference from said heat sink comprising: a) a solid,generally planar single layer polyimide substrate, said substrate havingfirst and second surfaces; and b) at least one layer of conformable,heat conducting paraffin-based material formed upon each of the firstand second surfaces of said substrate, said heat conducting materialbeing formulated to enhance the heat transfer from said electroniccomponent to said heat sink.
 2. The thermal interface of claim 1 whereineach said layer of conformable, heat conducting material is formulatedto have selective phase-change properties such that said material existsin a solid phase at normal room temperature, but melts when subjected totemperatures of approximately 51° C. or higher.
 3. The thermal interfaceof claim 1 wherein said conformable, heat conducting material comprises:a) 60% to 90% by weight of paraffin; b) 10% to 40% by weight ofgraphite; and c) up to 5% by weight of an ethylene vinyl acetatepolymer.
 4. A heat sink for dissipating heat transferred thereto by anelectric component comprising: a) a baseplate mounted to said electroniccomponent, said baseplate having a platform surface; and b) a folded-finassembly mounted upon said platform surface of said baseplate; and c) athermal interface disposed upon said platform surface, said interfacebeing comprised of a heat conductive substrate having a high dielectriccapability.
 5. The heat sink of claim 4 further comprising: a) a layerof thermally conductive material formed upon said platform surface ofsaid baseplate intermediate said folded-fin assembly, said heatconducting material being formulated to facilitate the transfer of heatfrom said baseplate to said folded-fin assembly.
 6. The heat sink ofclaim 4 further comprising: a) a compression apparatus attached to saidbaseplate for imparting a downwardly compressive force against saidfolded-fin assembly such that said folded-fin assembly is caused to becompressively bonded to said baseplate.
 7. The heat sink of claim 6wherein said compression apparatus comprises: a) an elongate pressureclip attached to said baseplate, said pressure clip being configured toextend over said folded-fin assembly when said folded-fin assembly ismounted upon said platform surface and impart a downwardly compressiveforce thereto to cause said folded-fin assembly to become compressivelybonded with said baseplate; and b) an electrically isolated pressurespreader positioned intermediate said pressure clip and said folded-finassembly, for evenly distributing the downwardly compressive forceimparted by said pressure clip upon said folded-fin assembly.
 8. Theheat sink of claim 7 wherein said pressure clip comprises an elongatemember having opposed ends and a downwardly extending leg and footformed upon each respective opposed end, said pressure clip furtherincluding an elongate mid-portion extending over said folded-finassembly for imparting a downwardly compressive force thereto, saidbaseplate further having formed thereon a pair of opposed slotsreceiving and interconnecting with a respective one of said feet of saidpressure clip.
 9. The heat sink of claim 6 wherein said compressionapparatus comprises: a) a plurality of said elongate pressure clipsattached to said baseplate; and b) a plurality of pressure spreaders,each respective pressure spreader being positioned intermediate adedicated one of said plurality of pressure clips and said folded-finassembly.
 10. The heat sink of claim 4 wherein said heat conductivesubstrate comprises a polyimide.
 11. The heat sink of claim 4 whereinsaid base plate is formed from an electrically conductive material, saidbase plate having formed thereon a ground contact connection.
 12. Theheat sink of claim 11 wherein said heat sink further comprises: a) alayer of thermally-conductive, electrically insulated materialinterposed between said base plate and said electronic component. 13.The heat sink of claim 12 wherein said layer of thermally-conductive,electrically insulated material comprises a thermal interface, saidthermal interface comprising a generally planar, non-electricallyconductive substrate having first and second surfaces and at least onelayer of conformable heat conducting material formed upon said first andsecond surfaces, said heat conducting material being formulated toenhance the heat transfer from said electronic component to said heatsink.
 14. The thermal interface of claim 1 wherein said conformable,heat conducting material comprises: a) 60% to 90% by weight of paraffin;b) 0% to 5% by weight of resin; and c) 10% to 40% by weight of anelectrically-conductive filler.